When a limb or twig of a plant is cut, the plant is injured. The injured plant immediately begins a process of damage containment and repair of the injury. This process includes a collapse of the damaged cells at the cut surface in an effort to reduce "bleeding." Bleeding results in a loss of plant fluids as drying of the exposed surface commences. Drying is not confined to the surface layer of cells at the cut. Often, cells as deep as half an inch within the plant experience fluid loss and drying. A reduction in such drying is generally believed to be beneficial to the healing process by allowing the plant to maintain higher moisture levels at the wound site and prevent such cells from dying. Such cells can then continue to grow and form callus tissue over the surface of the wound.
Various compounds and mixtures have been used on tree and shrub wounds to prevent drying and promote healing. Most are based on paint, shellac or asphalt-derived compounds. These compounds have generally been found to actually retard the healing process.
Lanolin has been recognized for many years as an effective pruning sealant. Lanolin is generally believed to promote healing by preventing drying and die-back, thereby allowing callus to form promptly at the wound edges. However, the viscosity of lanolin at temperatures in excess of about 70.degree. F. is so high that the lanolin tends to drip from a pruning site without forming a protective coating.
An extensive study of wound closure on trees was performed by McQuilkin in the 1940s, with the results published in the Journal of Forestry in 1950. Various sealing compositions were tested, including lanolin blended with rosin and/or pine gum. While found to be effective as a pruning sealant, lanolin blended with rosin and/or pine gum is a tacky mass which is difficult to manufacture, handle and apply. The blend also tends to remain tacky for days after application, with the tacky mass attracting and trapping a variety of insects at the application site.
Thus, there is an unmet need for a plant pruning sealant composition which is easy to apply and effective at typical environmental temperatures ranging from 40.degree. to 120.degree. F. for both reducing drying and die-back at a pruning site and preventing insects from accessing the pruning site.